Ni-cr hard facing alloys



United States Patent Ni-Cr FACING ALLOYS Lloyd F, Bowne, J13,Livingston, N. ,J., and Peter Payson, New York, N. Y assigiors-toCrucible ,Steel .Company if America, New York, N. Y., a corporation ofNew ersey No Drawing. Application July 30, 1951, Serial No. 239,388

4 Claims. (Cl. 75-171) Ibis invention pertains to nickel base alloys,utilizable pri ipally a a ha d a ng l y or in s m. and containing, tothis end, a relatively high carbon content, together with relativelyhigh chromium and boron, as .essential constituents.

It is an object of this invention to provide a low melting point, nickelbase alloy of high hardness and good corrosion resistance. It is afurther object of this invention to provide a corrosion resistant, hardfacing alloy which does not require either of the strategic alloyingelements cobalt or tungsten, although small amounts of each may bepresent, as noted below.

It is desirable that the melting point of the alloy be relatively low sothat the hard facing deposits of the alloy on a base metal can beapplied rapidly and with minimum consumption of fuel. The use of a lowmelting point alloy also permits deposition on relatively thin sectionsof a base metal with minimum distortion of the underlying section.

We provide hardness and wear resistance in our alloy by incorporatingcarbon, boron, and chromium in it so that chromium carbides and boroncompounds are present in the cast or deposited alloy. To contain thechromium carbides and boron compounds, we use nickel as a matrix,because nickel is less expensive and more readily available than cobalt,and nickel is much more corrosion resistant than iron.

In addition to providing hard compounds, carbon and boron lower thesolidus temperature of the alloy and cause a wide spread between'thesolidus and liquidus temperatures of the alloy. Boron also makes thealloy selffluxing. This combination of low melting point, wide rangebetween the solidus and liquidus temperatures, and self-fluxingproperty, makes it possible for the alloy of this invention to bedeposited from a cast rod thereof as a series of beads, by means of anelectric are, or gas welding procedure, and then to be molded into asmooth surface of desired configuration, by heating the deposit to aboutl9.0,0 to 2l 0 0 F., and applying pressure by means of a die. Thefluxing property of 'the alloy also makes it adaptable for makingdeposits by spraying with a metal pra gu The alloy of the invention has,for reasons explained below, the following broad, preferred, and optimumrange of composition:

1 In each case the aggregate amount of carbon and boron is at least 2.2%

One application for the alloy of this invention is the hard facing ofreciprocating-engine exhaust valves. Since in this application the alloycomes in contact with the products of combustion of gasoline containinglead compounds, it is essential that the alloy of this invention behighly resistant to corrosion by molten lead compounds. As a test forsuch resistance we immerse our alloy in liquid lead oxide at 1675 F. andhold it immersed for a period of 1 hour, after which we clean the sampleand measure it for weight loss per unit of area. As shown in Table I, wehave found that relatively large amounts of silicon and boron havedeleterious effects on the corrosion resistance of the alloy.

Table 1.Efiect of boron and silicon on corrosion resistance of hardfacing alloy in molten lead oxide at 1675 F.

Analysis, Percent Lolss 1n 1r. Alloy gmSJS'q C Si Cr B N1 in.

. 44 25. 3 1. 3 Balance 34-. 53 46 25.6 2. 2 Balance 55-. 63 46 25. 4 3.4 Balance 1. 4-3. 3 1. 22 26. 6 3. 2 Balance 5. 1-6. 7 48 25. 4 1. 3Balance 48-. 50 70 25. 4 2. 2 Balance 56-. 67 52 25. 7 3. 3 Balance 5.6-5.8 38 25.2 1.3 Balance 30-. 33 42 24. 7 2. 0 Balance 72-1. 1 29. 21.0 Balance 1. 0-1. 1 .36 25. 1 2. 5 Balahce 30-. 38 1. 78 24. 8 2. 7Balance 5. 2-5. 6 3. 05 25. 9 2. 8 Balance 5. 2-5. 3

On the basis of the above results, we limit the boron content in ouralloy to 2.5% maximum and the silicon content to 0.5% maximum when ouralloy is to be used in applications where excellent resistance tocorrosion in lead oxide is required. However, for other applicationswhere only general resistance to corrosion is required, We may use asmuch as 3.5% boron and as much as 1.5% silicon in our alloy.

In respect to corrosion in lead oxide, we have found that carbon in thealloy may be varied from about 0.2% to about 2.3% without much effect,as shown in Table 2.

Table 2.Eflect of carbon on corrosion resistance of hard facing alloy inmolten lead oxide at 1675 F.

Analysis, Percent Llois in r., Alloy gins/sq C Si Cr B Ni in.

. 24 26 26. 5 2. 2 Balance 18-. 19 38 48 26. 7 2. 2 Balance 35-. 36 5729 26. 3 2. 5 Balance 30-. 40 79 22 25. 8 2. 7 Balance 33-. 34 98 42 25.2 2. 5 Balance 30-. 46 1. 16 68 25. 4 2. 5 Balance 60-. 63 l. 38 36 25.l 2. 5 Balance 30-. 38 2. 11 16 25. 9 2. 7 Balance 42-. 81 2. 33 16 26.3 2. 8 Balance 60-. 78

effects of chromium, copper, and iron on the corrosion resistance of thealloy in molten lead oxide are shown in Table 3.

Table 3.Efiects of chromium, copper, and iron on carrosion resistance ofhard facing alloy in molten lead oxide at I675 F.

Analysis, Percent Lolsls m Alloy gash.

C Si Cr B Cu Fe Ni in.

. 16 15. 2 2. 6 Balance. 40- 46 18 19. 8 2. 6 Balance. 31- 53 .36 25.12. Balance. .38 24 29. 5 2.8 Balance- 28- 71 26 34. 8 2. 5 Balance-52-1. 1 .28 25.9 2.6 Balance. .39- .54 26 25. 9 2. 5 Balance- 55- 76 2425.8 2. 5 Balance. 66- .80 76 25.3 2. 3 Balance. 28- 67 .30 26.6 2.4Balance. .38- .39 22 26. 0 2. 6 Balance. 505. 9 31 25. 9 2. 7 Balance. 40 -5. 4

On the basis of the above results, we may have from 15 .to 35% chromiumin our alloy, but generally We prefer to hold the chromium content toabout 27% because the higher chromium alloys are more expensive and alsomore difficult to weld. These results also show that we may have up to10% copper in our alloy. Since copper is less expensive than nickel, itis a desirable addition in our alloy. However, when the amount of copperin the alloy exceeds about 10%, the alloy is diflicult to depositsatisfactorily by conventional hard-surfacing techniques.

Iron is a desirable addition to our alloy from the viewpoint of cost,first, because iron is much less expensive than nickel; and sewnd,because when the alloy contains iron, ferro-chromium may be used as themeans for providing chromium to the alloy rather than the much moreexpensive chromium metal. However, the results in Table 3 show that thecorrosion resistance of the alloy is deleteriously affected when theiron content is as high as 10%. We, therefore, limit the iron content ofour alloy to about 8% when the alloy is required to withstand corrosionin lead oxide. However, for applications where only general resistanceto corrosion is required we may use up to 20% iron in our alloy.

The melting point of our alloy is appreciably lowered as both the carbonand boron content increase as shown in Table 4.

Table 4.Efiect of carbon and boron on the melting point of hard facingalloy Analysis, Percent Approximate Alloy Melting o si Cr B Ni 2 1. 9155 25. 3 0. 5 Balance. 2, 325 1. 53 87 25. 0 1. 0 Balance. 2, 250 1. 8090 29. 2 1. 0 Balance. 2, 150 .69 .44 25. 3 1. 3 Balance. 2, 200 1. O1.48 25. 4 1. 3 Balance. 2, 125 1. 43 44 25. 5 1. 3 Balance. 2, 125 1. 8638 25. 2 1. 3 Balance. 2,050 24 26 26. 5 2. 2 Balance. 2, 100 38 48 26.7 2. 2 Balance. 2, 100 61 46 25. 6 2. 2 Balance. 2, 050 1. 02 70 25. 42. 2 Balance. 2, 050 1. 26 42 24. 3 2. 2 Balance. 2, 000 1. 85 42 24. 72.0 Balance. 2, 000 57 29 26. 3 2. 5 Balance. 2, 050 98 42 25. 2 2. 5Balance. 1, 975 1. 38 36 25. 1 2. 5 Balance. 1, 975 52 46 25. 4 3. 4Balance. 1, 975 1. 05 52 25. 7 3. 3 Balance- 1, 975 2.33 16 26. 3 2. 8Balance. 1, 975

On the basis of these results, we use a minimum of 0.5% carbon and aminimum of 1.3% boron in our hard facing alloy so that its melting pointwill be under 2150 F. Obviously, when the carbon is as low as 0.70%, theboron in the alloy would have to be about 1.5% in order to have amelting point under 2150 F. We, therefore, set a minimum of 2.2% for thesum of carbon plus boron.

Our hard facing alloy as deposited has a room temperature hardness whichmay be as low as Rockwell C32 or as high as C62, depending on the carbonand boron contents; the higher the sum of carbon plus boron, the higherthe hardness of the alloy as deposited. This room temperature hardnessis practically unaffected by heating the alloy to temperatures as highas 1600 F. The hardness of the alloy at elevated temperatures decreaseswith increasing temperature, but reflects the hardness at roomtemperature; the higher the room temperature hardness, the higher thehardness at any particular elevated temperature.

Although our alloy is used mainly in the form of cast rods for applyinghard surfaces by conventional welding techniques, it may also be used inpowder form and applied to the surface to be covered by spraying. Ouralloy may also be used in the form of castings made by usual foundrytechniques. Such castings would have high hardness, corrosion, andabrasion resistance, although they would be relatively brittle.

What we claim is:

l. A nickel base alloy containing about: 0.8 to 1.8% carbon, 1.3 to 2.5%boron, the sum of carbon and boron aggregating at least 2.2%, 20 to 27%chromium, up to 0.5% silicon, up to 5% each of copper and iron, up to 2%cobalt, up to 2% of metal of the group molybdenum and tungsten, and thebalance substantially nickel, characterized in having a melting pointunder 2150 F., a room temperature hardness within the range of aboutRockwell C 32 to 62, combined with high corrosion resistance and highhardness at elevated temperatures.

2. An alloy consisting essentially of about: 0.5 to 2.2% carbon, 1.3 to3.5% boron, the sum of carbon and boron aggregating at least 2.2%; 15 to35 chromium, up to 1.5 silicon, up to 10% copper, up to 20% iron, up to2% cobalt, up to 2% of metal of the group tungsten and molybdenum,balance nickel.

3. An alloy consisting of about: 0.8 to 1.8% carbon, 1.3 to 3% boron,the sum of carbon and boron aggregating at least 2.2%, 20 to 27%chromium, up to 1% silicon, up to 10% copper, up to 8% iron, up to 2%cobalt, up to 2% of metal of the group tungsten and molybdenum, balancenickel.

4. An alloy consisting of about: 0.8 to 1.8% carbon, 1.3 to 2.5 boron,the sum of carbon and boron aggregating at least 2.2%, 20 to 27%chromium, up to 0.5% silicon, up to 5% each of copper and iron, up to 2%cobalt, up to 2% of metal of the group tungsten and molybdenum, balancenickel.

References Cited in the file of this patent UNITED STATES PATENTS1,203,555 Brix Oct. 31, 1916 1,493,191 De Golyer May 6, 1921 2,030,342Wissler Feb. 11, 1936 2,289,641 Fetz July 14, 1942 2,292,694 JerabekAug. 11, 1942 2,322,507 Cole June 22, 1943 2,458,502 Cape July 11, 1949FOREIGN PATENTS 273,209 Canada Aug. 16, 1927 886,222 France Oct. 8, 1943OTHER REFERENCES Woldman et al.: Engineering Alloys, 2nd edition(Revised 1945), pub. by Amer. Soc. for Metals, page 448.

Woldman et 21].: Engineering Alloys, 3d edition (Revised 1954),published by Amer. Soc. for Metals, page 489.

1. A NICKEL BASE ALLOY CONTAINING ABOUT: 0.8 TO 1.8% CARBON, 1.3 TO 2.5%BORON, THE SUM OF CARBON AND BORON AGGREGATING AT LEAST 2.2%, 20 TO 27%CHROMIUM, UP TO 0.5% SILICON, UP TO 5% EACH OF COPPER AND IRON, UP TO 2%COBALT, UP TO 2% OF METAL OF THE GROUP, MOLYBDENUM AND TUNGSTEN, AND THEBALANCE SUBSTANTIALLY NICKEL, CHARACTERIZED IN HAVING A MELTING POINTUNDER 2150* F., A ROOM TEMPERATURE HARDNESS WITHIN THE RANGE OF ABOUTROCKWELL "C" 32 TO 62, COMBINED WITH HIGH CORROSION RESISTANCE AND HIGHHARDNESS AT ELEVATED TEMPERATURES.